Acromial and scapular spine fractures after reverse total shoulder arthroplasty

Abstract

Acromial and scapular spine fractures after reverse total shoulder arthroplasty occur predominantly as a result of bony insufficiency secondary to patient and intra-operative technical factors. The spectrum of the pathology can range from a stress reaction to an undisplaced or displaced fracture. Prompt diagnosis of these fractures requires a high suspicion in the postoperative patient with a clinical presentation of acute onset of pain along the acromion or scapular spine and/or deterioration of shoulder function. Conventional shoulder radiographs are frequently unreliable in identifying these fractures, especially if they are undisplaced. Computed tomography (CT) and/or single photon emission computed tomography/CT scans are useful imaging modalities for obtaining a definitive diagnosis. Early diagnosis and non-operative treatment of a stress reaction or undisplaced fracture is essential for preventing further displacement and potential disability. The management of displaced fractures is challenging for the orthopaedic surgeon as a result of high rates of mal-union or non-union, decreased functional outcomes, and variable results after open reduction and internal fixation. Strategies for preventing these fractures include optimizing the patient's bone health, correct glenoid baseplate screw length and position, and avoiding excessive deltoid tension. Further research is required to identify the specific patient and fracture characteristics that will benefit from conservative versus operative management.

Keywords: acromion; periprosthetic fractures; reverse total shoulder arthroplasty; scapula.

Figure 1.

A 71-year-old patient 16 months after reverse total shoulder arthroplasty with pain along the scapular spine. (a) Anteroposterior and (b) Trans-scapular views did not show a fracture. (c) Axial computed tomography (CT) scan showing a minimally displaced scapular spine fracture 6 weeks after the onset of symptoms.

Figure 2.

A 77-year-old patient 4 months after reverse total shoulder arthroplasty. Indicative views of serial computed tomography (CT) and single photon emission computed tomography (SPECT)-CT imaging. (a) CT scan at onset of symptoms did not demonstrate a fracture. (b) SPECT-CT demonstrates areas of increased uptake in acromion and arthritic acromioclavicular joint. (c) CT scan performed 6 weeks after initial presentation demonstrates the acromial fracture in the area identified on SPECT-CT. (d) Repeat CT at 3 months demonstrates sclerosis and callus formation.

Figure 3.

Classification of acromial fractures. Courtesy of Levy et al.

Figure 4.

A 61-year-old female patient who complained of anterior shoulder pain 12 months after a left reverse total shoulder arthroplasty (rTSA) for rheumatoid arthritis. At 3 months post-rTSA, she was diagnosed with a scapular spine stress fracture. This was treated conservatively and complete union occurred at 6 months. (a) Anteroposterior, (b) axillary and (c) trans-scapular views of the left shoulder 1 year after rTSA. (d) An axial computed tomography (CT) scan did not show a coracoid fracture. (e) A single photon emission computed tomography/CT scan showed increased uptake in the previous scapular spine fracture and base of the coracoid, consistent with an undisplaced coracoid stress fracture. This was treated conservatively and symptoms resolved after 3 months.